The present invention relates generally to an earth-moving machine, and, more particularly, to an earth-moving machine of the type having a single lifting arm.
Such earth-moving machines having a single lifting arm, commonly referred to as xe2x80x9ctelehandlersxe2x80x9d, adapt the single lifting arm for rotation relative to the frame itself and around a first shaft; and a loading unit, which is fitted such as to rotate relative to the lifting arm, around a second shaft, which is substantially parallel to said first shaft. U.S. Pat. No. 5,820,199 discloses a frame assembly for an operator""s compartment of a construction work machine, such as an earth-moving machine. The compartment has an upper roof portion, a lower base portion and first and second side support assemblies connected between the roof portion and the base portion mid-way along the length of the compartment. Each side support assembly includes a straight part, comprised of formed tube, and a curved part, formed of a fabricated box section having several individual wall plates.
The machine additionally comprises a first actuator cylinder, which can impart to the lifting arm oscillation around the first shaft; and an orienting device, which can maintain said loading unit in a pre-determined angular position during oscillation of the lifting arm, and comprises a second and a third actuator cylinder, which are connected to one another by means of a hydraulic circuit.
Said first and second actuator cylinders have respective longitudinal shafts which are substantially parallel to one another, are disposed adjacent to one another, and below the lifting arm, and are hinged both to the frame and to the lifting arm itself, at respectively a third and fourth shaft, which are substantially parallel to the first and second shafts; and the third actuator cylinder is accommodated inside an end portion of the lifting arm which projects downwards from, and is disposed transversely relative to, the lifting arm itself, and is pivoted both on the lifting arm and on the loading unit.
During oscillation of the lifting arm around the first shaft, the second actuator cylinder is controlled by the first actuator cylinder, and in turn, and by means of said hydraulic circuit, controls functioning of the third actuator cylinder, and thus, the angular position of the loading unit around the second shaft.
Since the end portion of the lifting arm must have dimensions which are pre-determined so as not to impede the view of the loading unit by an operator located in the driving cab of the machine, the dimensions of the third actuator cylinder are also determined, i.e. its cross-section and length, and thus the capacity of oil which must be contained inside said hydraulic circuit.
In addition, when the maximum amplitude of oscillation of the lifting arm around the first shaft, and the distance between said third and fourth shafts have been determined, the length of the first and of the second actuator cylinders are also determined.
It is apparent from the foregoing that, when the length of the second actuator cylinder and the capacity of the hydraulic circuit have been determined, the cross-section of the second actuator cylinder itself is also determined.
Consequently, the known machines of the above-described type have some disadvantages, the main one of which consists of the fact that, when the amplitude of the oscillation of the lifting arm, and the distance between said third and fourth shafts exceed pre-determined values, the cross-section of the second actuator cylinder becomes relatively reduced, and the second actuator cylinder can be bent under the, and/or be damaged by the, load generated on the second actuator cylinder itself by the lifting arm.
It is an object of the present invention to provide an earth-moving machine which is free from the above-described disadvantages.
These and other objects, features and advantages are accomplished according to the instant invention by providing an earth-moving machine is provided with a first actuator cylinder, which can impart to a lifting arm oscillation around a corresponding pivoting shaft, and with a second actuator cylinder, which can maintain a loading unit in a pre-determined angular position during oscillation of the lifting arm itself; the first and the second actuator cylinder being disposed adjacent and parallel to one another, and being connected mechanically to one another in order to increase the resistance of the second actuator cylinder to the load generated on the second actuator cylinder itself by the lifting arm.